1. Field of the Invention
The present invention relates to an assembly for setting a valve prosthesis in a corporeal duct, especially a cardiac valve and in particular an aortic valve.
2. Description of the Related Art
Documents WO 91/17720, WO 98/29057 and EP 1 057 460 each describe an assembly of this type, comprising the valve prosthesis to implant; a radially expandable reinforcement, called a “stent,” clean, in the expanded state, to bear against the wall of the target corporeal duct, this bearing allowing this stent to be immobilized with respect to this wall; and means for fixing the valve to the stent. Setting of the stent thus allows the valve to be installed in the corporeal duct, eliminating the necessity for outside access and thus for direct surgical intervention.
However, this technique may have important disadvantages leading to a risk of damage to the valve by the balloon utilized for expanding the stent, and limiting the expansion force that it is possible to give to the stent. This limitation has an effect on the anchoring of the stent, making a displacement of the assembly possible. This limitation also has an effect on the sealing of the stent at the valvular ring, which is particularly affected when the calcified areas give the valvular ring an irregular form and/or a certain rigidity. Expansion of the balloon may also lead to damage to the corporeal duct, particularly when the duct is in a blood vessel.
Furthermore, the target corporeal duct may not present a perfectly circular cross section at the implantation site, particularly when the natural valve is retained and when this valve, or valvular ring, comprises calcified areas. Whatever the degree of expansion of the stent, the circular shape of this stent then may not be suitable for the specific anatomy of the implantation site. A defect in sealing of the implanted valve may then result. Furthermore, the stent presents a certain rigidity, which leads to a rigidity in the implantation catheter. This rigidity may make the advancement of this catheter to the implantation site difficult.
Another disadvantage of the prior technique is the direct connection of the leaflets' commissures to the stent. A different than anticipated expansion of the stent, and thus of the valve, results, which may lead to a poor coaptation of the leaflets and thus a defective operation of the valve. The stent must consequently be subjected to a predetermined expansion that prevents, or makes difficult, the adaptation of this stent to the anatomic variability. The prior technique also has the disadvantage of, in cases of aortic valve implantation, inducing a risk of obstruction of the coronary ostia.